By Nathan Hodge, Olga Pavlova, and Julia Hollingsworth

Updated 0613 GMT (1413 HKT) June 21, 2019

In this aerial view taken on January 22, 2019, captured marine mammals are seen in enclosures at a holding facility in Srednyaya Bay in the Far Eastern town of Nakhodka.

Moscow (CNN)Russia is to begin freeing a small group of beluga whales and orcas held in a cramped pen, which some have dubbed whale jail” in the country’s far eastern coast.

The marine animals are among more than 100 whales which have been in Srednyaya Bay, near the city of Nakhodka, which is close to the North Korean border.

News of the planned release was announced Thursday, during a nationally televised call-in show with Russian President Vladimir Putin.

Two orcas — also known as killer whales — and six belugas will be transported to their place of release in the Sea of Okhotsk, Russian news agency RIA-Novosti reported, citing the Pacific Branch of the All-Russian Research Institute of Fisheries and Oceanography.

Russian prosecutors began investigating the whales in November last year, after images and videos released by environmentalists showed them living in crowded pens.

Commercial capture of killer whales is strictly regulated and allowed solely for educational and scientific purposes.

News of the so-called “whale jail” outcry  from animal rights activists, who said the captured whales were part of a million-dollar trade in marine animals to ocean theme parks in China.

During the call-in show on Thursday, Putin said the killer whales alone could be sold for about $100 million.

“The problem cannot be solved so simply: where there is a lot of money, there are difficulties with the solution,” he said, according to Russian news agency RIA-Novosti.